Antenna



Sept. 12, 1950 w. o. GORDY 2,521,844

ANTENNA Filed Nov. 16, 1945 IN V EN TOR. WALTER O. GOR DY BY ATTORNEYPatented Sept. 12, 1950 UNITED STATES O FFICE- v. Q 6 4 .1 I i I r f t II 7 Walter o. Gordy,Cambridge,Masss assignor, by?1 mesne assignments, tothe Unitedn ta e 9 America as represented by the Secretary of War 1Application November 16, Serial No. 629,151

, 4 Claims. (01. 250%3353) This invention relates to antennas and moreThe scanning actionmay beproduced entirely by electrical .means, ormaybe accomplished by mechanical motion, for, ex

ample by movement of the antenna itself'orof an element thereof.

A scanner devised by John S. Foster, application Serial No. 657,156,filed March 26, 1946, to which the instant invention is related, employswhat may be termed a conical shell Waveguide and. is hereinafterbrieflyconsidered inorderto betterdescribe the present ,i lVention.

In the Foster scanner, only a single-beam of electromagnetic. radiationis emitted at any one time. The presentinvention is an improvementthereon whereby two scanning beams of electro;

magnetic energy may be simultaneously directed from the one antennasystem. v

Among the objects of this invention are; ,to provide a single conicalshellwaveguide antenna which will scan two defined sectors of spaceseparately and simultaneously; an P i a conical shell waveguide. scannerwhich is compact in structure and light in weight, considering'the largesectors of space swept by the scanner.

features of this invention will become apparent from the descriptioncontained herein taken with the drawings accompanying thisspecification; in which:

Fig. 1 is a cross-sectional view of a Foster coni- -cal shell waveguidescanner; t v H c Fig. 2 is a cross-sectional view of a preferredembodiment of the present invention;

Fig. 3 illustrates in perspective the external appearance'of thewaveguide scannerof the'invention; and

Fig, 4 illustrates the geometry applicable to a radar system employingthe pres'entinvention. Referring. now to Fig. 1, 'there is illustrated across-sectional view of a conical shell waveguide Further objects and,,ethr advantages and defined sectorof space linearly. with time. at a 19rapid rate.

region where a conventional. waveguide transmission line 'connectsto aninner member of the scanner. The conical shell waveguide is formed byouter and inner members H andl2 providing substantially parallel outerand inner conical surfaces l3 and M, respectively. The sepa-''rationbetween surfaces l3 and His preferably less than .one-halfwavelength 'atthe contem plated operating frequencies. Inthe describedembodiment of this Foster scanner, member 1 I is stationary, and member.[2 is .rotatable about longitudinal aperture; is provided. inthe inneror rotor member I2, .as shown, extending 'substantiallyalonglinearelements of conicalsurfac'eM. A similar longitudinal apertureI1 is provided in outer member I l, extending substantially along linearelements of conical surface l3. Energy may be introduced to the systemthrough a waveguide I8 extending coaxially into the rotor 'memb'er: ofthe structure and communicating with a branching waveguide l9. .Energymay be-fed into or extracted from the rotor memher" by use of a rotatingjoint, not shown,:pro-.

'vided' at one end of waveguide l8. .Waveguide i9 is secured to therotonmember l2, and at directed toward a third reflecting surface shapedin the form of a-parabolic cylinder: of comparatively small height.-'Wave energy directed into suchastructur'e-toward the reflecting surface,from theneighborhood of thefocal line defined by the'par' 'abolicsurface, wil'lbe'. reflected with a wavefront normal to the axialplaneof theparab o lic'surface. Pillbo'x?! is-such a' structure, ex- "ceptthat hereits surfaces "-arecurved or de formed, in order'toifit withinrotor. land in order to provide an emanating wave front at longi-'tudinal pertu e-15' which corresponds with the open end'terrnination ofpillbox' l2f Theemanatin wave front 'at' aperture I Em'ay be substan:tiallyparallel to the line; elements" of conical s'ur face [4 ataperture l 6. The feed j apertdiefzo tr waveguide I9 is located intheneighborhoodof the focal'point of the parabolic reflecting surface :2of'pillboxlzg' I I A series'of'teethln, adapted to reflect or directclockwise direction and is refiectedintoiaperture 32 by reflecting teetha; likewise; electromag -netic energy fed from branching-waveguide 44 topillb'ox 42 is-directed by reflecting teeth-Mbinto conical shellwaveguide 29, traveling clockwise "therethrough until directed out'ofaperture' 32 by reflecting teeth 35b. As inner member-3i of thestructure is rotated, electromagnetic'energy emanates from aperture 32in two separate beams which recurrently scan, in. the sameplane, sectorswhich have substantially equal anglesin the embodiment illustrated The.salient members 35 and 40- are arranged to slip past each other so thatcontinuous rotation may be achieved." If

:desired, two separateaperturesmay. be utilized forthe transmission :ofenergy from waveguide 2.9,

instead of using an aperture 'dividedzby a partition, as shown.Similarly, two angular-1y. separated apertures maybe .utilizedfforthetransmls- :sion of energy into conical waveguide 29,.rather.than-using adjacent apertures 31'.and;38 as in the embodiment hereindisclosed. It will be understood that arranging the apertures andreflectors as shown, however, permits use of a single re- .flectgrilluminated by .theenergy from-both. apertures. A

Referring now to Fig. 3, there is illustrated in perspectii 'e theexternal appearance of the conical shell waveguide scanneriof Fig. 2,likez'parts having like reference numerals appliedzthereto. The outersurface of member 30 may be conical in shape to conform to its innersurface 33. An

auxiliary reflector may be used to increase the effective gain of theantenna system. Thus, a parabolic cylinder reflector 50 may be utilized,held in fixed relation to the scanner structure proper by members 5| asshown. Reflecting surface 52 of the parabolic cylinder reflector 5| mayhave its focal axis substantially along the line of aperture 32. Such aportion of the parabolic cylinder surface may be used that the reflectedelectromagnetic waves travel outwardly therefrom in a plane spaced fromand parallel to the axial plane of the parabolic cylinder, so that theconical waveguide scanner may be in a non-interfering position relativeto the reflected beams.

The conical waveguide scanner of Fig. 2 may be constructed so that thetwo radiated beams may scan separate sectors, as angle A and angle B ofFig. 3. This result may be accomplished in the embodiment hereindisclosed by suitably orienting the structure of pillboxes 4| and 42within the rotor member 3|. If linear arrays, lens systems, or othermeans are utilized for providing electromagnetic energy having planeWave fronts at longitudinal apertures in the inner surface of theconical shell waveguide, a similar effect may be accomplished by properphasing or alteration of the elements thereof.

It will be assumed, as before, that rotor member 32 turns in a clockwisedirection as seen in Fig. 2 of the drawing.

Referring again to Fig. 3, lines A-l and A--2 respectively indicate, forthe two positions of the rotor wherein salient members 40 are positionedimmediately clockwise and counterclockwise, respectively, relative tosalient members 35, the directions which may be taken by energy whichhas traveled in a counterclockwise direction through waveguide 30.Similarly, lines 3-! and B-2 respectively indicate the directions whichmay be taken by energy which has traveled in a clockwise directionthrough wave guide 29.

Thus the cycle of scan for sectors A and B in the disclosed embodimentstarts with the beams ai ing-cycle. 11 Theutility'of such a'two-sectorscanning struc ture Lmay be understood by reference to 4which-illustrates the geometry of a radio echo detection ,and ranging:system using :theconical in/positions A-=-| and B-l'," the beamssweeping toward the positions A2- andB-f-I during the scanningcycl'e,-':andlstarting 'again'frdmiposltions .A l 'and-B l.-Jat thebeginning of thenext'sc shell: waveguideiscanner herein disclosednAvessel .60 is diagrammed navigating surface waters. Thestructureillustrated in:Fig.=3 may be mount -:ed on vessel 60.;withaperture:32. and ir'eflector: 50 .inpaigenerallyverticalposition.) InFigs! are .dia

gramm'ed;thecsectors having angles A..and IB;-::-'It

will lbehobserved therefrom thattheibeamaaof energy sweeping sector Bmay start alongl-ar line r B-l, which is substantially.-horizontal,andtsweep through-a sectonB. c. Similarly; theeother-beam maystart alongav substantially yerticallineAe-wl and sweep througha sector Ahavinga:like angle."

At the completion of a scanning -cycle; :.the t'wo beamsgmay .be.substantially-.7 codirectional; Izas shown. 'Ihe antenna structure may.beirevolved in azimuthto obtainooverage of an entireseg-j mentof spaceabout; vessel 60.. {Ifhe systemdee scribed may .thus simultaneouslyvsatisfy ,1in; gen-r eral; the {requir men s f both .adoneganse and-renegsyste rorhthebeam. sweepinathe ow r ev n sector B caniarryiereaterzpower.

or gre ater antenna gaimthan tha swe ping the f (In practical radarsystems, far-distant targets, requiring greater higher elevation sectorA.

may thus be accomplished by use of the present invention. A furtheradvantage resides in the complete coverage of the total angle A plus B.which is otherwise difllcult to secure.

4 In a radar system utilizing the antenna structure here described,echoes returned from distant Objects may be located in elevation bytheir timed relationship to the period of the scan. The scanning islinear with the rotation of the rotor, so that with the rotor turned ata constant speed, the angular displacements of the beams are linear withtime. Consequently, such timed relationship may be established throughthe use of linear sweep circuits, as well as other means, synchronizedwith the rotor rotation. Moreover,

signals returning from both beams may be simultaneously displayed on asingle oscilloscope designed to display the signal range as plottedagainst elevation angle.

Although the description and discussion of the conical waveguide scannerhas here been considered from the viewpoint only of energy radi-" atedfrom the scanner it will be apparent to those;-

skilled-inthe radio art that the scanner is a linear device, which willtransmit energyequally well in a reverse direction with like directiveIn other words, as already assumed in connection with the discussion ofFig. 4, where qualities.

signals are both sent and received by the radar system antenna, theconical shell wave guide scanner of the invention may be used equally.

well and with like directive qualities for either transmission orreception of electromagnetic energy.

The scanner or this invention may also be def l ke 'SBImG SGTGtOES,-.so= that the-,scanning= angle is cnvened byeboth; beams-:crossingeachwother. This designirmightbe useful in 'locating bymadar a hiddensource of shell fire by observing the echoes retmmedaat angles whichindicate the path'ionorbit=offithe projectile. The presentinmentiomthusqaiffordssa convenient :means f or ;providingjzaad'oublebeam itoisatisfy the requirements ofrmany'electromagnetic radiationsystems.

Nariations in the" retructure herein :described as canrxembodiment of.:the invention will be apparent tb those'skiHedz init'he radio andwaveguide arts. Therefore it'ais .not desired to restrict theinventicmito the precise embodiment-herein dis- Mosedmorito :theparticular usage herein .de-

scfiibei,

- 21].. #1A.'i waveguide structure iofiel'ectromagnetic enegyyiinehidin'g :imier and 'outer n'iembersdefining 22a substantially'conical shell waveguide, 5am in'zier'=member providing the innersurface-of isaid m'oiiieal ishell: waveguide and having awe longitudinal'inrier apeitures therein, said outer member :providing the outercoaxial surface of r saixl cconical' si'iell waveguide and having twolefig'itudinal outer apertures therein-inner surfaceeneizgy-idirectirigi members arranged between saiiitliiin'er "aperturesand extending into said conical shellwaveguide from said inner member,za'iid out'er surfaee energydirecting members ;-8 arranged:be.tween.'said mu ter zap'erturesgand 1e15- itendingwintogsaidsteonical .shel-l wave uide 12mm .saidioutermembemwherebmenergzniayibetranslf-EBIGd between eaiehfiof said, inner'-1suri ace (ape;-sturesand areal-"responding;;outer-;su1;fi'aee apertureicireumferentially through said conical-g -shell Waveguide q:TheWaveguide=-structurerof c1aim:.-1=wherein e-saidfinnernnember': and" itsenergy-directirig; members .arearotxatablewajbout theeconmiomaxisoiisaid (coaxial :surfia'ces, :and wherein :said (eIiH/ yfidi':rectingrmembers are'lin the zior'maof teethwa'dapted [to 'slipipasteach rather lupon-zrotation oft-said inner'member.

iThewaveguideustructure *oi"claim s1 .wherein saidiinnerr member'.andiits energyeiiireetingrinemberszrare rotatable about thecommomaxistofnsaid coaxialisutfacesw e (r55:

Thefwaveguidmstructurecof claim d iurther including means withinv-saiddrmier 'rstmmturez ibr transferringcenerg'y-:thmugh said'innerapertures.

'WMEBER-TOJGQRDY.

v 1 EEEERENeEsemEn The wwwmg references la re' of record m the file oithis patent:

